The present invention relates to process variable transmitters of the type used in industrial process control and monitoring systems. More specifically, the present invention relates to compensation of a sensor output in a process variable transmitter using a Hysteron basis function.
Industrial process control and monitoring systems typically use devices known as process variable transmitters to sense various process variables. For example, processes can be used in the manufacture, processing, transportation and storage of various process fluids. Example process variables which are monitored include temperature, pressure, flow rate, level within a container, and pH, among others. These process variables are sensed using a process variable sensor of the process variable transmitter. In a typical configuration, the process variable transmitter transmits information related to the sensed process variable to another location, such as a central control room.
In order to monitor operation of the process with certainty, it is important that a particular process variable be accurately sensed. One type of error which can arise in sensing a process variable is related to an effect known as hysteresis. This hysteresis effect can cause the output from a process variable sensor to have more than one possible state for a particular value of a process variable being sensed. Thus, the hysteresis effect can lead to inaccurate measurement of a process variable. One technique to address this hysteresis effect is to design process variable sensors which exhibit reduced hysteresis. However, it may not be possible to completely eliminate the hysteresis effect or such a design may compromise other aspects of the process variable sensor.